This invention relates to elevated-temperature electronic-test systems, and more particularly to robotic testers for memory modules including SIMMs and DIMMs.
A variety of electronic systems including personal computers (PCs) use DRAM memory chips mounted on small, removable memory modules. Older single-inline memory modules (SIMMs) have been replaced with dual-inline memory modules (DIMMs), and 184-pin RIMMs (Rambus inline memory modules) and 184-pin DDR (double data rate) DIMMs. New kinds of memory modules continue to be introduced.
The memory-module industry is quite cost sensitive. Testing costs are significant, especially for higher-density modules. Specialized, high-speed electronic test equipment is expensive, and the greater number of memory cells on high-speed memory modules increases the time spent on the tester, increasing test costs.
Handlers for integrated circuits (ICs) have been used for many years in the semiconductor industry. Handlers accept a stack of IC chips that are fed, one at a time, to the tester. The tested IC is then sorted into a bin for IC chips that have passed or failed the test. Handlers have also been developed for memory modules.
Rather than use an expensive general-purpose I.C. tester, inexpensive testers based on PC motherboards have been developed. These motherboard-based testers cost only about $10 K while replacing a quarter-million-dollar I.C. tester. The memory module to be tested is inserted into a test socket on a test adapter board (daughter card) mounted on the back-side of the motherboard. Special handlers can be used for module insertion.
Elevated-temperature testing is often desired to more thoroughly screen for defects. Hot air can be blown onto the memory module being tested. Ideally, the motherboard itself is cooled while the memory module under test is heated. See the parent application, xe2x80x9cConnector Assembly for Testing Memory Modules from the Solder-Side of a PC Motherboard with Forced Hot Airxe2x80x9d, U.S. Ser. No. 09/702,017, now U.S. Pat. No. 6,357,023.
FIG. 1 highlights funneling hot air to the memory module being tested, while the motherboard inside a chassis is cooled. A conventional PC motherboard is mounted upside-down within chassis 60. Rather than connect motherboard substrate 30 directly to chassis 60, as in a conventional PC, motherboard substrate 30 is mounted to metal plate 64 by standoffs or spacers 61. Motherboard substrate 30 is not mounted directly to chassis 60 in this embodiment, although it could be in some embodiments. Screws, bolts, or clamps (not shown) can be used to secure metal plate 64 to chassis 60.
Test adapter board 50 is mounted to well 66, while well 66 is mounted to metal plate 64. Test socket 51 is mounted to test adapter board 50, while pins 52 provide electrical connection from test socket 51 to motherboard substrate 30. The memory module 18 being tested is inserted into test socket 51. Test adaptor board 50 provides electrical connection from the module-under-test (MUT) in the SIMM/DIMM test socket 51 to the leads for the removed SIMM socket on the PC motherboard.
Motherboard substrate 30 has components 42, 44 (I.C. chips, sockets, capacitors, etc.) mounted on component-side 32 of substrate 30. Memory modules 36 are SIMM or DIMM modules that fit into SIMM/DIMM sockets 38. SIMM/DIMM sockets 38 (hereinafter SIMM sockets 38) have metal pins that fit through holes in substrate 30. Expansion cards 46 are plugged into expansion sockets that are also mounted onto component-side 32 of substrate 30. Cables 48 and expansion cards 46 are bulky but do not interfere with a robotic arm inserting memory module 18 into test socket 51 since cables 48 and expansion cards 46 are mounted below substrate 30, while test socket 51 is mounted above substrate 30. Cables 48 and expansion cards 46 are kept out of the way inside chassis 60.
Test adapter board 50 is a small circuit board that allows an automated handler, a person, or a robotic arm easy access to SIMM/DIMM test socket 51 that is mounted on test adaptor board 50. Test socket 51 on one surface of test adapter board 50 mates with connectors on SIMM/DIMM memory module 18, the module-under test. The other surface of adaptor board 50 has adapter pins 52 inserted in holes to make electrical contact. These adaptor pins are soldered into through-holes in adaptor board 50 and in substrate 30. Adapter pins 52 are arranged to have the same arrangement and spacing as the substrate-mounting pins for SIMM sockets 38. One or more of SIMM sockets 38 has been removed from the component side of the PC motherboard, leaving the through-holes. Adapter pins 52 are then fitted through the exposed through holes for the removed SIMM socket. Rather than push the pins through from component-side 32, adapter pins 52 are pushed through from solder-side 34 to component-side 32.
Top plate 75 can be mounted to chassis 60 in a variety of ways, such as by standoffs or metal guides or brackets. Top plate 75 has an opening to allow access to test socket 51 so that a robotic arm can insert and remove memory module 18 from test socket 51.
When environmental testing is desired, heated air is forced between top plate 75 and metal plate 64. This heated air blows past memory module 18 when it is inserted into test socket 51. The heated air warms memory module 18 to an elevated temperature. When memory module 18 is heated, it is typically more likely to fail than when at room temperature. Such elevated-temperature testing provides a margin or guard-band to the test, so that the passing memory modules are more reliable than modules tested at room temperature.
Cooling fan 71 is provided in chassis 60 to cool motherboard substrate 30 and its components 42, 44 and expansion cards 46. Even air at room temperature can be effective at cooling the motherboard if a sufficient volume of air is blown past the motherboard""s components. Components such as integrated circuits heat up during operation and benefit from such cooling. Of course, reduced-temperature air could also be blown into chassis 60, such as air from outside a building in a cold climate.
Since metal plate 64 separates motherboard substrate 30 from test adapter board 50, the cooling air from cooling fan 71 is separated from the heated air blown against memory module 18 under test. Test adapter board 50 is mounted within well 66 and forms a sufficient seal to prevent the cooling air within chassis 60 from cooling memory module 18 being heated and tested.
Top plate 75 can be replaced with a tube, rectangular pipe, or air guide that blows hot air directly on memory module 18. This may provide a more efficient air flow. Temperature sensors such as thermocouples could be added near the test socket. Chassis 60 can be provided with slots, holes and openings to allow for air flow to motherboard components 42, 44 and expansion cards 46. Multiple cooling fans can be used.
A larger chassis with multiple openings on the top, each for holding a metal plate 64 with a motherboard and test adapter board can be used. This allows for parallel testing using several motherboards and test sockets.
FIG. 2 is an overhead diagram looking down on a multi-motherboard test station with overhead rails for an x-y-z robotic handler. See the parent application, Automated Multi-PC-Motherboard Memory-Module Test System with Robotic Handler and In-Transit Visual Inspection, U.S. Ser. No. 09/660,714. Operator 100 can sit in front of the test station, controlling operation with a touch-screen or keyboard. Trays of untested memory modules can include a barcode that is scanned in to main system interface 65 by operator 100 before the tray is put into input stacker 63. Robotic handler 80 then picks untested modules that are moved over to input tray 62 by stacker 63. The modules are first inserted into leakage tester 82. Modules that pass are then moved by robotic handler 80 to the test socket on the test adaptor board on the solder-side of one of motherboard substrates 30 for testing.
Modules that fail the motherboard or leakage test are placed on repair tray 76 by robotic handler 80. Modules passing the motherboard test are pulled from the test socket by robotic handler 80 and moved in front of cameras 75 for visual inspection. Modules failing visual inspection are dropped into VI tray 78. Passing modules are placed on output tray 72 and full trays are moved by stacker 73 to the front of the test station where operator 100 can remove them.
Each of the motherboards fits into a well in the frame of the test station. The test station has a surface at about bench-top level composed of the exposed solder sides of the motherboards in the wells in the frame. Robotic handler 80 rides on rails 92, 94 mounted above the level of the motherboards, such as above the head of a seated operator 100. Operator 100 also replaces repair tray 76 and VI tray 78 with empty trays when full.
Fixed rails 92, 94 in the x direction allow movable y-rail 96 to travel in the x direction. Robot arm assembly 98 then travels in the y direction along y-rail 96 until robot arm assembly 98 is directly over the desired position, such as a test socket on an adaptor board, or an input or output tray. An elevator arm on robot arm assembly 98 then moves up and down, pulling out (up) a module or inserting a module into (down) a test socket or tray. Robot arm assembly 98 can also rotate or spin the module into the desired position.
What is desired is a heating system for a multiple-motherboard robotic test system. A method of heating memory modules being tested in a robotic tester is desired. Good temperature control is desirable.